What is a pregnancy test?
A pregnancy test is a device that identifies the presence of the hormone beta-HCG, produced by the cells of the developing placenta 6 to 10 days after fertilization. This hormone can be detected in urine or blood, and reaches a level that confirms pregnancy as early as the first day of delayed menstruation.
When to take a pregnancy test?
1. First day of menstrual delay: Most tests are optimal from the first day of menstrual delay for increased accuracy, although some ultra-sensitive tests can detect pregnancy a few days earlier.
2. Morning, the ideal time: We recommend testing in the morning, with the first urine of the day, when HCG is most concentrated. If this is not possible, wait at least three hours after your last micturition.
3. Wait to reduce false negatives: For those who suspect pregnancy but receive a negative result, it's advisable to wait a week to retest or consult a healthcare professional.
Types of pregnancy test
Urine tests: These are the most common tests and can be carried out at home. They work by detecting HCG in urine, and are renowned for their accuracy if used correctly. Depending on the type of test, it may be necessary to :
- Place the strip under the urine stream.
- Collect the urine in a container and dip the strip in it.
- Use a dropper to place a few drops of urine into a test cassette.
Blood test: performed in a laboratory or at your doctor's, this measures not only the presence of HCG but also its exact quantity, which is useful for assessing the progress of the pregnancy or in the event of specific suspicions (such as an ectopic or multiple pregnancy). Note that blood test results can be positive a few days after implantation.
How reliable are pregnancy tests?
Most available urine pregnancy tests are 99% accurate if instructions are followed to the letter. However, reliability can be compromised in the following cases:
- Taking the test too early: Testing before menstrual delay can give false negatives.
- Drug interference: Some fertility treatments containing HCG may cause false positives.
- Personal factors: Irregular cycles can delay egg implantation, delaying HCG production.
How to interpret results
1. Positive result: It is advisable to confirm the result by making a medical appointment. A blood test and ultrasound scan will confirm the pregnancy and initiate prenatal monitoring.
2. Negative result but persistent delay: If menstruation does not occur, retesting after a few days or consulting a professional is recommended. Certain medical conditions can cause menstrual delay independently of pregnancy.
Common mistakes to avoid with a pregnancy test
To ensure the accuracy of your pregnancy test, here are a few mistakes to avoid:
- Missing the recommended time: Waiting until the menstrual period is over ensures greater reliability.
- Not following instructions: Each test has its own specificities, and mistakes can lead to erroneous results.
- Drinking too many fluids before the test: This can dilute the HCG in the urine, making the test less sensitive.
Pregnancy tests are reliable and accessible tools for the rapid detection of pregnancy. For optimum results, it is advisable to respect the recommended time limits and interpret the results according to the manufacturer's instructions. If in doubt, consult a healthcare professional to ensure appropriate follow-up.
Good to know
In the case of IVF, beta-HCG tests are requested a few days after the transfer.